Re: changing email for existing contact
This really depends on whether you were selling to the “individual” or the “business” - as a best practice, if someone leaves a company and your communications were related to that company, you wouldn’t want to update that record to their new company or it could cause the deals, meetings, etc. to not be accurate.
If you’re selling to individuals, it’s a little different and I would say “company” is significantly less important overall.
I would create a new contact with their new email, and if you feel you need to combine, use the merge contacts tool to clean up your data every quarter or so.
or…if you know you want the same record, create their new contact, merge with their old, and everything is up to date.
I tagged you on another post about using associated company in reporting, just thought it might be helpful.
I don’t know that you’ll need to code your own CRM, if you want to share more about your specific use case, I’d be happy to share recommendations for how I would leverage HubSpot’s available tools. It’s possible you’re trying to do something “the hard way” and it could be simplified.